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CALM DOWN!. -24 LKFS. Show. -24 LKFS. Show. -21 LKFS. ?. -24 LKFS. Show. -21 LKFS. Downmix Dilemma. ?. Ls. L. Lf. Surround Mix. C. Rf. R. Rs. Frequent Downmix. Producers Stereo Deliverables Networks Stereo Channels & Internet Distribution Stations

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Presentation Transcript

-24 LKFS

Show


-24 LKFS

Show

-21 LKFS


?

-24 LKFS

Show

-21 LKFS


Downmix dilemma
Downmix Dilemma

?

Ls

L

Lf

Surround Mix

C

Rf

R

Rs


Frequent downmix
Frequent Downmix

  • Producers

    • Stereo Deliverables

  • Networks

    • Stereo Channels & Internet Distribution

  • Stations

    • Stereo Infrastructure & Channels

  • Consumers

    • Stereo STBs & TVs (≥61%)


Downmix dilemma1
Downmix Dilemma

?

Ls

L

Lf

C

?

Surround Mix

Rf

R

Rs

?


Preserve center
Preserve Center

L

0 dB

Near Field

C

Surround Mix

+6 dB

R

Average

+3 dB


Preserve center1
Preserve Center

?

Ls

L

Lf

C

Surround Mix

-3 dB

Rf

R

Rs

?


Preserve rear
Preserve Rear?

Ls

L

Lf

Can't Hear Dialog!

C

Surround Mix

-3 dB

Rf

R

Rs


Adjust rear
Adjust Rear

Ls

-3 dB

L

Lf

C

Surround Mix

-3 dB

Rf

R

Rs

-3 dB


Defacto standard downmix
Defacto Standard Downmix

Ls

-3 dB

L

Lf

C

Surround Mix

-3 dB

R

Rf

Rs

-3 dB


Defacto compatible surround mix
Defacto-Compatible Surround Mix

C

70 dB SPL

L

C

-3 dB

70 dB SPL

R


Incompatible surround mix
Incompatible Surround Mix

Power Sum

10*Log(3) = 4.8 dB

74.8 dB SPL

Lf

C

Rf

Voltage Sum

20*Log (1+.7) = 4.6 dB

Power Sum

10*Log(2) = 3 dB

77.6 dB SPL

2.8 dB Error!

L

Lf

C

-3 dB

Rf

R


Bottom line
Bottom Line

  • If two ads are mixed in surround to measure -24 LKFS…

  • One can sound and measure 2.8 dB louder after downmix

  • Producers can "game" the system to be louder

  • Stations and MVPD's could be deemed non-complaint when broadcasting "compliant" content!

  • Not a problem when content mixed to be compatible

  • A real problem for some Public Television music shows

  • See AES e-Brief 38 for measured statistics "The Effect of Downmixing on Measured Loudness"



Customize the downmix
Customize the Downmix

Power Sum

10*Log(3)

74.8 dB SPL

Lf

C

Rf

Voltage Sum

20*Log (1+.2) = 1.8 dB

Power Sum

10*Log(2) = 3 dB

74.8 dB SPL

L

Lf

C

-12 dB

Rf

R


Producer controlled metadata
Producer-Controlled Metadata

Producer

Consumer

Ls

Lf

Left

C

AC3

AC3

Surround Mix

AC3 Encoder

AC3 Decoder

Right

Rf

Audio +

Metadata

Audio +

Metadata

Rs

LFE

Manual Metadata


Tv station controlled metadata
TV Station-Controlled Metadata

Producers

Networks

TV Stations

Consumers

Ls

Lf

Left

C

AC3

AC3 Decoder

Surround Mix

Distribution

Plant

AC3 Encoder

Right

Rf

Audio +

Metadata

Rs

LFE

X

X

X

No Metadata Channel!

See ATSC A/85 Chapter 7


Why no metadata channel
Why No Metadata Channel?

  • Many producers lack interest and ability in setting metadata

  • For a show, requires adoption by ALL distributors

  • Within a network, requires adoption by EVERY station

  • Within a station, requires adoption in ALL equipment

  • Most equipment requires obscure custom settings

  • Some equipment cannot carry metadata

  • Penalty of metadata error is severe: loss of center channel!

*

*

*I'll buy you a beer if you'll let me whine about it.


Proposed solution
Proposed Solution

  • Standardize downmix for systems without metadata

    • -3 dB for Center and Rear

  • Require loudness measurement of the standard downmix

    • Encourages producers to mix appropriate to standard downmix

    • Producers can use film-style mixing or shift center channel phase

    • Penalty of an inappropriate mix is merely a show softer in surround

  • Change delivery standards

  • Modify A/85

  • Ask LKFS meter vendors to include downmix measurement



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